Unmanned vehicles capable of environmental interaction

ABSTRACT

An unmanned aerial vehicle (UAV) system is disclosed. The UAV system includes a chassis, a plurality of propeller assemblies configured to provide vertical take-off and landing (VTOL) for the chassis with propulsion in 6 degrees of freedom including along a cartesian coordinate system (X, Y, Z) and provide yaw, pitch, and roll, the plurality of propeller assemblies are selected from the group consisting of (i) two fixed propeller assemblies and a tiltable propeller assembly, and (ii) four fixed propeller assemblies, a boom having a boom propeller assembly, configured to selectively provide positive and negative rectilinear thrust vectors, and an end-effector coupled to a distal end of the boom, the end-effector having a force sensor configured to provide contact force between the end-effector and an object.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of a U.S. application Ser. No.16/109,873 titled UNMANNED AERIAL VEHICLES CAPABLE OF ENVIRONMENTALINTERACTION which was filed on 23 Aug. 2018, which is related to andclaims the priority benefit of U.S. Provisional Patent Application Ser.No. 62/550,199 filed Aug. 25, 2017, the contents of each of which ishereby incorporated by reference in its entirety into the presentdisclosure.

STATEMENT REGARDING GOVERNMENT FUNDING

This invention was not made with government support.

TECHNICAL FIELD

The present disclosure generally relates to unmanned aerial vehicles(UAVs), and in particular for UAVs capable of interacting with theirenvironments.

BACKGROUND

This section introduces aspects that may help facilitate a betterunderstanding of the disclosure. Accordingly, these statements are to beread in this light and are not to be understood as admissions about whatis or is not prior art.

Unmanned aerial vehicles (UAVs) are ubiquitous. These are found inmyriad applications (e.g., inspection, surveillance, mapping, andprecision farming, etc.). In these applications, the UAVs are operatedin both a manual mode, whereby a pilot remotely pilots the UAV andoperates controls on the UAV, as well as an autonomous mode, whereby theUAV's own controller plots a trajectory and autopilots the UAV to aplace of interest as well operates various devices (e.g., an on-boardcamera).

Nowadays, more is expected from a UAV design. In particular, there is aninterest for a UAV to interact with its environment. For example, somedesigns include object manipulation, such as pickup and release,transportation, as well as other inspection tasks requiring at leastpart of the UAV to make contact with an object.

To accomplish these tasks, vertical take-off and landing (VTOL) UAVs arenow found in myriad applications. A common VTOL UAV is a quadcopter,which has four rotors. In most of the VTOL UAVs, however, due to costconstraints, UAVs do not decouple movement in all the desired degrees offreedom. Referring to FIG. 1, a schematic of a UAV is shown with desired6 degrees of freedom. The six degrees of freedom include back-and-front,left-to-right, up-and-down, pitch, roll, and yaw. However, in mostcases, these six degrees of freedom are not decoupled and provided to acontroller as independent degrees of freedom. As such, there is aninherent coupling between the UAVs translational and rotational dynamicsand thus it is unable to independently control the forces and torques inall dimensions. This lack of independence in the six degrees of freedomresults in inability to control arbitrary velocities in a space definedby all six degrees of freedom. For example, a UAV may be hovering in adesired plane, i.e., being controlled on a plane defined by axes X-Y-Z(3 degrees of freedom) but unable to precisely maintain that plane andpropel forward and backwards in order to perform a tedious task.

Therefore, there is an unmet need for a novel approach to control UAVssuch that these vehicles can perform tedious tasks within an environmentby decoupling propulsion in a plurality of degrees of freedom.

SUMMARY

An unmanned aerial vehicle (UAV) system is disclosed. The UAV systemincludes a chassis and a plurality of propeller assemblies configured toprovide vertical take-off and landing (VTOL) for the chassis withpropulsion in 6 degrees of freedom including along a cartesiancoordinate system (X, Y, Z) and provide yaw, pitch, and roll. Theplurality of propeller assemblies are selected from the group consistingof (i) two fixed propeller assemblies and a tiltable propeller assembly,and (ii) four fixed propeller assemblies. In the case of the two fixedpropeller assemblies and a tiltable propeller assembly, the two fixedpropeller assemblies are disposed on port and starboard and are coupledto the chassis, each coupled to a propeller, and the tiltable propellerassembly is disposed on tail and coupled to the chassis and a propeller,having a motor for tilting with respect to a vertical axis. In the caseof the four fixed propeller assemblies, the four fixed propellerassemblies are disposed on port, starboard, fore, and tail and arecoupled to the chassis, each coupled to a propeller. The UAV systemfurther includes a boom having a boom propeller assembly, configured toselectively provide positive and negative rectilinear thrust vectors. Inaddition, the UAV system includes an end-effector coupled to a distalend of the boom, the end-effector having a force sensor configured toprovide contact force between the end-effector and an object.

A method of operating an unmanned aerial vehicle (UAV) systems is alsodisclosed. The method includes providing vertical take-off and landing(VTOL) by propelling the UAV along six degrees of freedom includingalong a cartesian coordinate system (X, Y, Z), yaw, pitch, and roll byutilizing a plurality of propeller assemblies selected from the groupconsisting of (i) two fixed propeller assemblies and a tiltablepropeller assembly, and (ii) four fixed propeller assemblies. In thecase of the two fixed propeller assemblies and a tiltable propellerassembly, the two fixed propeller assemblies are disposed on port andstarboard and are coupled to the chassis, each coupled to a propeller,and the tiltable propeller assembly is disposed on tail and coupled tothe chassis and a propeller, having a motor for tilting with respect toa vertical axis, and. In the case of the four fixed propeller assembliesthe four fixed propeller assemblies are disposed on port, starboard,fore, and tail and are coupled to the chassis, each coupled to apropeller. The method also includes propelling the UAV along arectilinear vector, utilizing a boom having a boom propeller assembly,configured to selectively provide positive and negative thrust. Inaddition, the method includes interfacing with the UAV's environment byproviding an end-effector coupled to a distal end of the boom.Furthermore, the method includes sensing contact force between the endeffector and an object by a force sensor coupled to the end effector.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic of an unmanned aerial vehicle (UAV) operatingabout six degrees of freedom.

FIG. 2 is a photograph of a UAV system according to the presentdisclosure showing a tricopter having a propeller chassis, a controller,and a flight controller.

FIG. 3 is a perspective schematic of the propeller chassis of FIG. 2showing three propeller heads and a boom propeller assembly.

FIG. 4 is a perspective view of the boom propeller assembly of FIG. 3.

FIG. 5 is a flowchart showing the steps for accomplishing a first taskby the UAV system of the present disclosure.

FIG. 6 is a flowchart showing the steps for accomplishing a second taskby the UAV system of the present disclosure.

FIGS. 7A, 7B, 7C, 7D, 7E, and 7F are photographs of the UAV system ofthe present disclosure operating the second task according to FIG. 6while the UAV system is on the ground.

FIGS. 8A, 8B, and 8C are photographs of the UAV system of the presentdisclosure operating the second task according to FIG. 6 while the UAVsystem is in the air.

FIG. 9 is a block diagram of control blocks showing theinterconnectivity of the controller and the flight controller of FIG. 2and a disturbance controller block interacting with actuators on the UAVsystem of the present disclosure.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of this disclosure is thereby intended.

In the present disclosure, the term “about” can allow for a degree ofvariability in a value or range, for example, within 10%, within 5%, orwithin 1% of a stated value or of a stated limit of a range.

In the present disclosure, the term “substantially” can allow for adegree of variability in a value or range, for example, within 90%,within 95%, or within 99% of a stated value or of a stated limit of arange.

A novel approach to control UAVs such that these vehicles can performtedious tasks within an environment by decoupling propulsion in aplurality of degrees of freedom is disclosed. Referring to FIG. 2, aphotograph of an unmanned aerial vehicle (UAV) system 100, according tothe present disclosure, is shown. The UAV system 100 is in the form of atricopter (i.e., three propulsion mechanisms—discussed below, e.g.,propellers, adapted to provide propulsion for flying), however, otherapproaches such as a quacopter. In each of these approaches, the UAVincludes propellers with vertical take-off and landing (VTOL)capabilities. The UAV system 100 includes a flight controller 102 (notvisible at the angle shown but provided under the component with thewhite strip), propeller assembly 103-i—there are 3 propeller assemblies(i.e., i=1, 2, 3) in the UAV system 100 shown in FIG. 2, a boompropeller assembly 104, landing base 105-i—there are 2 landing bases(i.e., i=1, 2) in the UAV system 100 shown in FIG. 2, one or morebatteries 106 (collectively referred to as battery 106), a controller108, and an end effector 110. It should be noted that the propellerassemblies 103-1 and 103-2 are fixed, and the propeller assembly 103-3is capable of being tilted by including a servo motor, as describedfurther below. Each of the propeller assemblies 103-i is coupled to abase platform 102 which also houses the flight controller 102, thebattery 106, and the controller 108. The flight controller 102 andcontroller 108 are shown as two different controllers (the former tomanage flight of the UAV system 100, and the latter to manage operationsof the boom propeller assembly 104), however, the functions in these canbe performed in a single controller (not shown). The landing base 105-iis an inverted T-shaped assembly that is coupled to the base platform101 and is adaptable to allow the UAV system 100 to land securely on asurface. The boom propeller assembly 104 terminates in an end-effector110 adaptable to interface with the UAV's environment, as describedfurther below.

Referring to FIG. 3, a perspective view of a propeller chassis 150 isshown. The propeller chassis 150 is the backbone of the propellerassembly 103-i and the boom propeller assembly 104, providing thoseassemblies with a structure from which these assemblies can extendoutwards. The propeller chassis 150 includes a base 152, which includesone or two plates upon which and coupled to are other components such asthe base platform 101, the flight controller 102, the landing base105-i, the battery 106, and the controller 108. Each of the propellerassemblies 103-i (see FIG. 2) extend out of the base platform 101 at anequi-angle with respect to one-another—in the case of the tricoptershown in FIGS. 2 and 3, the angle (not shown) is 120°. In addition, eachof the propeller assemblies 103-i (see FIG. 2), includes propeller shaft154-i—there are 3 propeller shafts (i.e., i=1, 2, 3) in the propellerchassis 150 shown in FIG. 3, terminating at a propeller head 158-i—thereare 3 propeller heads (i.e., i=1, 2, 3) in the propeller chassis 150shown in FIG. 3. In addition, a boom shaft 158 extends out of the baseplatform 101 which is coupled to a boom propeller head 160, which iscoupled to the end effector 162.

A cartesian coordinate system is shown atop the base 152, indicatingthree degrees of freedom (i.e., along X—forwards and backwards; alongY—side-to-side; and along Z—up and down). While not shown, roll, pitch,and yaw are the other three degrees of freedom (example shown in FIG.1), which can be achieved by a right-handed rotation about the X, Y, andZ axes, respectively. At the end of each propeller head 158-i, is avector identified by t. For example, the propeller head 158-1 has avector identified as t_(r) for the right-side thrust, the propeller head158-2 has a vector identified as t_(l) for the left-side thrust, andpropeller head 158-3 has a vector identified as t_(t) for the tail-sidethrust. The propeller head 158-3 with its t_(t) thrust vector can betilted (as shown with angle α) with respect to a vertical line passingthrough the center of the propeller head 158-3. Similarly, the boompropeller head 160 has a vector identified as t_(b) for the boom thrust.The boom propeller head 160 can generate a positive or negative thrust(t_(b)) by rotating its associated propellers clockwise orcounter-clockwise, causing the UAV system 100 (see FIG. 2) to pushforward or pull backwards.

It should be appreciated that the propeller heads 158-i can includeelectrical motors (e.g., direct current or alternating current motors),each independently rotating with respect to one another. On the otherhand, each propeller head 158-i can be a gearbox translating rotationalmotion within or by the propeller shaft 154-i from a main gearbox (notshown) in the base 152 to the associated propeller of the propeller head158-i. In addition, it should be appreciated that the boom propellerheads 160 can include an electrical motor (e.g., direct current oralternating current motors), independently rotating with respect toother propeller heads. On the other hand, the boom propeller head 160can be a gearbox translating rotational motion within or by the boomshaft 156 from a main gearbox (not shown) in the base 152 to the boompropeller head 160.

Referring to FIG. 4, a closer perspective view of the boom propellerassembly 104 is provided. Propellers 172 are coupled to the boompropeller head 160, capable of generating forward/reversed thrusts basedon the direction of rotation (clockwise, counter clockwise). Asdiscussed above, the boom propeller assembly 104 includes a boom shaft156 coupled to the boom propeller head 160 via a bearing 172. The boomshaft 156 terminates at a collar 174 to which the end effector 162 iscoupled. The end effector 162 can be constructed according to one ormore embodiments. In the embodiment shown, the end effector 162 includesa force sensor 180 capable of providing a force signal to the controller108 so that it can adjust the forward/reverse boom thrust t_(b),discussed above.

In the embodiment shown in FIG. 4, the boom propeller assembly 104 alsoincludes an electric motor 176, that is coupled to a timing pulley 178which is coupled to an interface gear 179. The motor 176 via the timingpulley 178 can rotate the propellers 172 independent from the otherpropellers coupled to the propeller heads 158-i.

The UAV system 100 can operate in two modes: the tricopter mode where itmoves similar to a conventional UAV without engaging the boom propellerhead 160, and the boom propeller mode where when the UAV system 100 isgenerally hovering at a desired position, it uses the boom propellerhead 160 for forward/reverse motion.

Referring to FIG. 5, a flowchart 200 providing steps in controlling theboom propeller head 160 is depicted. The control embodiment shown is forthe UAV system 100 to perform the task of attaching a sensor (e.g., avibration sensor) to a desired location (e.g., a bridge). The UAV system100 is initially maneuvered using a manual operation as shown in block202 and maneuvered to a desired position (e.g., in proximity to astructure). At this point, the controller 108 enters into an autonomousmode to accomplish the task (i.e., placing a device on a structure). Inblock 204, the controller 108 along with the flight controller 102maneuver the UAV system 100 to within about 1.5 meters of a targetplaced on a structure. The UAV system 100 can determine distance from atarget by utilizing a sonar sensor, known to a person having ordinaryskill in the art, on the end-effector 162, a UAV mounted RGB-D sensor,known to a person having ordinary skill in the art, that provides depthinformation, or by tracking a landmark of known size in an RGB cameraimage from a camera mounted to the UAV, a technique known to a personhaving ordinary skill in the art. Using a vision system, describedbelow, the controller 108 along with the flight controller 102 maneuverthe UAV system 100 to center a target positioned on the structure withina view field as shown in block 206. At this point the controller 108actuates the boom propeller head 160 to cause the UAV system 100 toapproach the target, as shown in block 208. Once the end effectorassembly 162 has made contact with the structure, as shown in block 210,the boom propeller head 160 is placed in a throttle position to apply aprescribed force to a sensor onto the structure. The force sensor 180 atthe end of the end effector assembly 162 provides a feedback signal tothe controller 108 in order to determine the throttle percentage of theboom propeller head 160. Once the sensor has been installed on thestructure, as shown in block 212, the controller 108 reverses therotation of the boom propeller head 160 to cause the UAV system 100 toretreat from the structure. Thereafter, as shown in block 214, thecontroller 108 and the flight controller 102 move the UAV system 100 apredetermined distance away from the structure and maintains hover atthat position, awaiting resumption of flight by a pilot. Once the pilotmoves the UAV system 100 out of the autonomous mode, it is placed backin the manual mode, as shown in block 216.

Referring to FIG. 6, as well as FIGS. 7A-7F, a flowchart 300 and photosproviding steps in controlling the boom propeller head 160 is depicted,for accomplishing a second task. The control embodiment shown is for theUAV system 100 to perform the task of opening a door to an electricalpanel. The UAV system 100 is initially maneuvered using a manualoperation as shown in block 302 and maneuvered to a desired position(e.g., in proximity to electrical panel). At this point, the controller108 enters into an autonomous mode to accomplish the task (i.e., openingthe door of the electrical panel). In block 304, the controller 108along with the flight controller 102 maneuver the UAV system 100 towithin about 1.5 meters of the door. The UAV system 100 can determinedistance from a target by utilizing a sonar sensor, known to a personhaving ordinary skill in the art, on the end-effector 162, a UAV mountedRGB-D sensor, known to a person having ordinary skill in the art, thatprovides depth information, or by tracking a landmark of known size inan RGB camera image from a camera mounted to the UAV, a technique knownto a person having ordinary skill in the art. Using a vision system,described below, the controller 108 along with the flight controller 102maneuver the UAV system 100 to align gripper associated with the endeffector assembly 162 with the door, as shown in block 306, and as shownin FIGS. 7A, 7B, and 7C (which represent photos of an on the grounddoor-opening task undertaken by the UAV system 100 in the autonomousmode) or as shown in FIG. 8A (which represent a photo of an in-airdoor-opening task undertaken by the UAV system 100 in the autonomousmode). At this point the controller 108 actuates the boom propeller head160 to cause the UAV system 100 to approach the door, detect collisionwith the door and the end of the end effector assembly 162 and grip thehandle on the door, as shown in block 308, and as shown in FIG. 7D, andFIG. 8B. Once the end effector assembly 162 has gripped the handle, asshown in block 310, the boom propeller head 160 is placed in a throttleposition in the reverse direction to apply a prescribed pull force tothe handle on the door, as shown in FIG. 7E. The force sensor 180 at theend of the end effector assembly 162 provides a feedback signal to thecontroller 108 in order to determine the throttle percentage of the boompropeller head 160. Once the door is opened, as shown in block 312 andas shown in FIG. 7F and FIG. 8C, the controller 108 and the flightcontroller 102 moves the UAV system 100 to retreat to a point near thedoor. Thereafter, as shown in block 314, the controller 108 and theflight controller 102 move the UAV system 100 a predetermined distanceaway from the structure and maintains hover at that position, awaitingresumption of flight by a pilot. Once the pilot moves the UAV system 100out of the autonomous mode, it is placed back in the manual mode, asshown in block 316.

Referring to FIG. 9, a block diagram 400 for autonomous controlling ofthe UAV 100 system is shown. Disturbances for the UAV system 100 includeexternal (e.g., wind), and internal (i.e., the torque exerted onto theUAV system 100 when the boom propeller head is activated). A disturbancecontroller 402, which can be part of the controller 108 or the flightcontroller 102, receives data from an inertial measurement unit (IMU)(not shown), known to a person having ordinary skill in the art. Basedon the apriori knowledge of the boom propeller head 160 actuation andknown torques exerted on the UAV system 100 thereby to distinguishbetween external and internal disturbances, as shown in block 402. Thedisturbance controller further receives as input the desired positionand the signals associated with the current position and resolves asolution for the controller, as shown in block 404. As shown in block406, the controller communicates with the flight controller, and it (oroptionally the controller—that path not shown), determine actuationsignal for the actuators as shown in block 408, which determine thecurrent position. This information is then provided to the disturbancecontroller.

A vision-based control system using the OpenCV 3.0 framework was usedfor accomplishing tasks discussed herein. The size, shape, and aspectratio of the door panel and door handle are predefined in an algorithm.The incoming video stream from a camera attached to the end effectorassembly 162 is first converted into a stream of grayscale images. Afteran edge detection process, known to a person having ordinary skill inthe art, the algorithm produces a closed contour image to match thepredefined sizes/shapes of the door panel and/or handle. Detectedcontours that do not match are discarded. Centroids for the contourimages are calculated next. Based on the position of the centroids,size/shape, and aspect ratios of the contours, and the (fixed) positionof end effector assembly 162 in the image, the appropriate commands aresent to controller 108 which provides the appropriate commands for themotor 176.

While, the UAV system 100 (see FIG. 2) disclosed here includes threepropeller head assemblies with the boom propeller, other configurationssuch as a quadcopter assembly is also possible. For example, aquadcopter can provide thrust vectors in all six degrees of freedom (seeFIG. 1), while a boom propeller can provide a rectilinear thrust vectorwhen the quadcopter is hovering at a desired position to accomplish thetask discussed herein (e.g., attach a device, e.g., a vibration sensor,to an object, e.g., a bridge, or gripping an object, e.g., a doorhandle, and moving the object, e.g., opening the door). As such, otherUAV configurations known to a person having ordinary skill in the artare also possible.

Those having ordinary skill in the art will recognize that numerousmodifications can be made to the specific implementations describedabove. The implementations should not be limited to the particularlimitations described. Other implementations may be possible.

1. An unmanned ground-based system, comprising: a chassis; a pluralityof wheels coupled to the chassis and configured to allow the chassis tomove about a surface; a plurality of propeller assemblies configured toprovide on-ground motion propulsions in 4 degrees of freedom includingalong a Cartesian coordinate system (X and Y), the plurality ofpropeller assemblies each having a propeller include two fixed propellerassemblies disposed on port and starboard which are coupled to thechassis, each coupled to a propeller; a boom having a boom propellerassembly with a propeller disposed on a plane generally perpendicular tothe propellers of the plurality of propeller assemblies, configured toindependently and selectively provide positive and negative rectilinearthrust vectors; and an end-effector coupled to a distal end of the boom,the end-effector having a force sensor configured to provide contactforce between the end-effector and an object, wherein the contact forceis used as a feedback signal to determine magnitude of the positive andnegative rectilinear thrust vectors that is generated by the propellerof the boom propeller assembly.
 2. The unmanned ground-based system ofclaim 1, the boom propeller assembly configured to rotate a boompropeller in a plane that is about perpendicular to a plane on which thepropellers of the fixed propeller assemblies rotate.
 3. The unmannedground-based system of claim 2, the end-effector further comprising anarrangement for performing a first task.
 4. The unmanned ground-basedsystem of claim 3, wherein the task is attaching a device to an object.5. The unmanned ground-based system of claim 4, wherein the device is asensor and the object is a bridge.
 6. The unmanned ground-based systemof claim 2, the end-effector further comprising an arrangement forperforming a second task.
 7. The unmanned ground-based system of claim6, wherein the second task is gripping a handle coupled to a door andopening the door.
 8. The unmanned ground-based system of claim 1,wherein each of the fixed propeller assemblies and the boom propellerassembly is operable by one of i) a dedicated motor, and (ii) a gear boxutilizing a direct drive coupled to the chassis.
 9. The unmannedground-based system of claim 8, wherein the dedicated motor is a directcurrent motor.
 10. The unmanned ground-based system of claim 8, whereinthe dedicated motor is an alternating current motor.
 11. A method ofoperating an unmanned ground-based system, comprising: providingon-ground motion propulsions in 4 degrees of freedom including along aCartesian coordinate system (X and Y) by utilizing a plurality ofpropeller assemblies each having a propeller including two fixedpropeller assemblies disposed on port and starboard which are coupled toa chassis, each coupled to a propeller; propelling the unmannedground-based system along a rectilinear vector, utilizing a boom havinga boom propeller assembly with a propeller disposed on a plane generallyperpendicular to the propellers of the plurality of propellerassemblies, configured to independently and selectively provide positiveand rectilinear negative thrust vector; interfacing with the unmannedground-based system's environment by providing an end-effector coupledto a distal end of the boom; and sensing contact force between the endeffector and an object by a force sensor coupled to the end effector,wherein the contact force is used as a feedback signal to determine themagnitude of positive and negative rectilinear thrust vectors that isgenerated by the propeller of the boom propeller assembly.
 12. Themethod of claim 11, the boom propeller assembly configured to rotate aboom propeller in a plane that is about perpendicular to a plane onwhich the propellers of the fixed propeller assemblies rotate.
 13. Themethod of claim 12, further comprising: performing a first task by theend-effector.
 14. The method of claim 13, wherein the task is attachinga device to an object.
 15. The method of claim 14, wherein the device isa sensor and the object is a bridge.
 16. The method of claim 12, furthercomprising: performing a second task by the end-effector.
 17. The methodof claim 16, wherein the second task is gripping a handle coupled to adoor and opening the door.
 18. The method of claim 11, wherein each ofthe fixed propeller assemblies and the boom propeller assembly isoperable by one of i) a dedicated motor, (ii) and a gear box utilizing adirect drive coupled to the chassis.
 19. The method of claim 18, whereinthe dedicated motor is a direct current motor.
 20. The method of claim18, wherein the dedicated motor is an alternating current motor.